The present invention relates, in general, to telecommunication and data communication systems and, more particularly, to an apparatus, method and system for multimedia access network channel management in a hybrid optical fiber and coaxial cable communication system.
The Internet Protocol (IP) has emerged as a dominant standard for packet data networks, as evidenced by, among other things, the rapid growth of electronic mail (email) systems and communication utilizing the World Wide Web. This rapid growth has fostered the demand for high-speed, broadband access networks, which both provide high-speed packet data transmission, for video, text, web pages and other data, and provide traditional telecommunication services, such as telephony (voice), facsimile (fax) and TDD (Telecommunications Device for the Deaf) transmission (collectively xe2x80x9cmultimediaxe2x80x9d). Various broadband access networks have been proposed, such as under the DOCSIS and CableLabs standards, which utilize a full duplex (two-way) capable hybrid optical fiber and coaxial cable (xe2x80x9chybrid fiber/coaxxe2x80x9d) network to deliver high speed Internet access, telecommunication services and other multimedia to homes, offices, and other premises.
Presently in such a hybrid fiber/coax network being developed by 3Com Corporation, a centralized, primary device known as a cable modem termination system (xe2x80x9cCMTSxe2x80x9d) (also referred to as a telephony modem termination system) broadcasts transmissions to multiple subscriber devices referred to as cable modems (xe2x80x9cCMsxe2x80x9d), for data transmission, and cable telephony modems (xe2x80x9cCTMsxe2x80x9d), not only for data transmission (identical to a CM) but also adding telephony capability such as xe2x80x9cplain old telephony servicexe2x80x9d (xe2x80x9cPOTSxe2x80x9d). Transmissions from the CMTS to the CMs and CTMs are referred to as downstream transmissions. Transmissions from multiple CMs and/or CTMs to the CMTS are referred to as upstream transmissions. In such networks, upstream and downstream transmissions are typically asymmetric, with a greater capacity provided in the downstream direction.
Access to such networks is typically provided based upon various requests transmitted to the CMTS by the various CMs and CTMs; accordingly, such networks may be referred to as xe2x80x9caccess networksxe2x80x9d. Following a grant of access, typically by the primary device such as a CMTS, upstream transmissions utilize a combination of frequency division multiplexing (xe2x80x9cFDMxe2x80x9d) and time division multiple access (xe2x80x9cTDMAxe2x80x9d), with any given upstream transmission channel specified by a transmission frequency and one or more time slots.
One of the challenges for a hybrid fiber/coax network is providing a user or subscriber with a quality of service equivalent to the service provided by the current public switched telephone network (xe2x80x9cPSTNxe2x80x9d). Specifically, users of the current PSTN have come to expect that the telephone system is highly available and the user is able to place calls whenever they desire, i.e., the user does not experience xe2x80x9cblockingxe2x80x9d by a lack of capacity within the network. One example of this user expectation occurs when a user experiences an emergency and dials a 911 emergency service. Simply stated, while blocking has occurred during widespread geographic emergencies, such as during the California earthquakes of the late 1980s and early 1990s, there is generally sufficient system capacity that a user of the current PSTN expects to be immediately connected to emergency services after dialing 911. As a result of this user expectation, the PSTN has been designed to provide sufficient capacity and minimal blocking.
Hybrid fiber/coax networks and systems, using a combination of FDM and TDMA for upstream transmissions, are challenged to provide users such immediate access on demand to the FDM/TDMA channels. This challenge is exacerbated when the CTM provides for broadband data transmission and multiple lines of POTS, with the CTM expected to be used for all communication needs, including connection to emergency 911 services, fax services, TDD services, and data services.
As a consequence, a need remains for an apparatus, method and system which provides for access network management, to provide a level or quality of service comparable to the PSTN, while simultaneously providing broadband multimedia transmission capability. Such an apparatus, method and system should provide for a minimal potential blocking of emergency calls and voice calls. In addition, such an apparatus, method and system should provide for optimal data transmission, including optimal fax and TDD quality. Such an apparatus, method and system should be user friendly, user transparent, and capable of implementation within existing hybrid fiber/coax networks.
An apparatus, method and system are provided for multimedia access network channel management, such as channel management in a hybrid fiber-coaxial cable network, for voice (telephony), video, fax and data transmission. The preferred system embodiment includes a plurality of multimedia transmission devices or multimedia modems, such as cable telephony modems (xe2x80x9cCTMsxe2x80x9d) or cable modems (xe2x80x9cCMsxe2x80x9d), for such voice (telephony), video, fax and data transmission, and includes a multimedia termination system or device, such as a cable modem termination system (xe2x80x9cCMTSxe2x80x9d). The multimedia termination system provides the access network channel management, defining which multimedia transmission devices may transmit and receive information at any given time. In addition, the multimedia termination system provides for access to broader networks, such as packet-based networks and to the public switched telephone network (xe2x80x9cPSTNxe2x80x9d).
For upstream communication from the CTMs to the CMTS, the network provides a plurality of channels, formed by a combination of frequency division multiplexing and time division multiple access. In the preferred embodiment, channels are utilized for two types of services, a reserved (or dynamic) services, having a constant bit rate, such as for telephony, fax and data services, and best efforts services, having a variable bit rate, such as for data services (such as email and internet activity). A CTM may gain access to the network through a poll from the CMTS, followed by transmitting a request, or without a poll from the CMTS, by transmitting a request utilizing a contention methodology. The various requests for either type of service (reserved or best efforts) are referred to generally herein as multimedia network access messages or simply as access requests, and include dynamic service requests (of various forms), best efforts requests, and gate messages (from a call management server).
Of particular significance, the present invention utilizes three major concepts in multimedia channel management. First, given that CTMs are constrained to transmit on a single carrier frequency at a given time, all of the various, mixed multimedia services for a given CTM are managed on a total, complete and non-independent basis, with potentially multiple channels allocated and managed on a single carrier frequency for the given multimedia transmission device. For example, if a given multimedia transmission device is currently engaged in a data transmission session and a telephony line goes off hook, a channel for the telephony line will be assigned to the same carrier frequency as the data session in progress. Also for example, in the event that a given CTM having two voice calls and a best efforts data transmission need to be moved to another carrier frequency (such as to accommodate a 911 call or a high bandwidth transmission from another CTM), then this entire group of services (voice plus data) for the given CTM are managed and moved together, as an aggregate, rather than piecemeal. The various embodiments of the present invention utilize a sophisticated searching and priority mechanism to move and manage all such channel usage, in order to provide a vacant channel on a particular carrier frequency, if needed.
Second, multimedia transmission is managed on both a polled and a best efforts basis, with specific polling utilized to prevent blocking, and with an additional best efforts service utilized to maximize system throughput for variable bit rate data transmissions. For example, through either a response to a poll or via contention, a multimedia transmission device may reserve a network channel for a particular type of service, such as telephony. During the time interval between reservation of the service and activation of the reserved service, the reserved channel may be utilized for best efforts services, such as variable bit rate data transmission.
Third, various comparative priorities are implemented to effectively ensure that certain types of services, such as 911 emergency access calls, are not blocked due to system capacity, and also to ensure that other services, such as fax, are of optimal quality. For example, to ensure non-blocking of 911 calls, in the event that the system is operating at full capacity, a lower priority service will be removed (or deleted) from a channel, to create a vacated channel for use by a 911 call. In addition, these priorities are utilized to determine whether particular services will be moved or deleted from assigned channels, to create capacity for higher comparative priority services. These various priorities may be individually determined by a service provider to accommodate any particular requirements of a subscriber.
When a CMTS receives a multimedia network access message or other access request having a comparative priority from a CTM, the CMTS determines whether there is a first channel which is available from the plurality of channels, and if so, assigns a first transmission corresponding to the access request to the first channel. When there is no available first channel, the CMTS determines whether there is a second transmission on a second channel which is moveable to a third channel, and if so, reassigns the second transmission to the third channel and assigns the first transmission corresponding to the access request to the second channel. For example, a first CTM may be engaged in a data communication, and may need an additional channel on the same carrier frequency for a voice communication. If all of the time slots (channels) on the carrier frequency are in use, the CMTS may move a transmission from one of the channels to a different carrier frequency, to make an available channel for the first CTM. In the preferred embodiment, certain transmissions, such as fax and TDD, are not moveable to another carrier frequency, while other transmissions, such as voice and data, are freely moveable to other channels and frequencies.
The CMTS also provides that certain types of services are non-blocking, such that when the network is operating at capacity, a lower comparative priority service or transmission will be interrupted or disconnected to allow a higher comparative priority transmission access to the system, such as an emergency (911) telephone call. As a consequence, when there is no available first channel and no second transmission which is moveable, the CMTS determines whether there is a third transmission on an assigned channel having a lower comparative priority than the comparative priority of the access request, and when there is a third transmission, the CMTS removes the third transmission from the assigned channel to form a vacated channel, and assigns the transmission corresponding to the access request to the vacated channel.
Other features of the present invention include the use of the CMTS to delay the third transmission, and following completion of the transmission corresponding to the access request, to allow resumption of the third transmission on the assigned channel. In addition, to maximize data throughput, the CMTS is further configured to reserve a fourth channel for a constant bit rate transmission, and prior to the commencement of the constant bit rate transmission, to allow utilization of the fourth channel for a variable bit rate transmission.
Yet another significant feature of the present invention occurs when a CMTS receives a second access request for a comparatively high bandwidth transmission. When this occurs, the CMTS determines a second plurality of channels consisting of a plurality of time-continuous channels having the comparatively high bandwidth, reassigns a plurality of transmissions, the plurality of transmissions previously assigned to respective channels of the second plurality of channels, to a corresponding plurality of channels which are not time-continuous; and the CMTS then assigns a transmission corresponding to the second access request to the second plurality of channels.
Numerous other advantages and features of the present invention will become readily apparent from the following detailed description of the invention and the embodiments thereof, from the claims and from the accompanying drawings.